The invention relates to a method of operating a cellular telecommunication system wherein one base station communicates with at least one mobile station, wherein the transmission includes at least two channels, and wherein the power level of the transmission is increased and decreased by requests of the mobile station. The invention also relates to a corresponding cellular telecommunication system and a base station.
In Direct Sequence Code Division Multiple Access (DS-CDMA) cellular telecommunication systems, a mobile station communicates in a so-called macrodiversity mode with a number of base stations. In order to keep the power levels of the combined signal received by the mobile station from the base stations at least similar, an inner-loop transmission power control is established. This control creates a transmission power control (TPC) signal which is sent from the mobile station to the base stations. Each one of the base stations then increases or decreases its power level depending on the TPC signal.
DS-CDMA telecommunication systems usually include a data channel (DPDCH) and a control channel (DPCCH). The power levels of these two different channels are increased and decreased in conjunction. This may lead to disadvantages, in particular in the downlink direction.
It is an object of the invention to provide a method for operating a telecommunication system which has an improved control of the power level of the transmission.
For a method as described above, this object is solved according to the invention in that one of the two channels is turned off if the power level of the transmission reaches a first maximum value. For a telecommunication system as described above, this object is solved accordingly by the invention.
If the first maximum value is reached it may be assumed that the base station is not able to satisfy the needed power to be received by the mobile station. In this situation, it may as well be assumed that the transmission from the base station to the mobile station is not received well at the mobile station. Therefore, it makes no sense to continue the transmission.
The invention is able to recognize this situation and then to consequently turn off the transmission from the base station to the mobile station. Thereby, the power consumption of the base station is reduced and other mobile stations are not disturbed anymore by the turned-off transmission.
It is advantageous if the one of the two channels is only turned off if the power level of the transmission reaches the first maximum value and if the mobile station still requests a further increase of the power level.
The inventive method thereby includes the additional feature that the transmission is only turned off, if the mobile station still requests for a further increase of the power level. However, if this is not the case, the transmission is not turned off. This means in other words, that the invention provides another trial whether the mobile station still needs more power after the first maximum value is reached. With this further trial it is possible to avoid the turn-off of a transmission, if the power level requested by the mobile station does not exceed the first maximum value too much.
Furthermore, it is advantageous if the power level of the other one of the two channels is limited to a second maximum value. As well, it is advantageous if the one of the two channels is turned on again if the power level of the transmission becomes smaller than the second maximum value or than a turn-on value which is smaller than the second maximum value.